fix(VirtualScroll): initialize trackByFn reference (#11624)
fix(VirtualScroll): initialize trackByFn reference (#11624)

* fix(VirtualScroll): initialize trackByFn reference

* fix(VirtualScroll): simplify fix for TrackByFn reference

TillaTheHun0/ionic,alan-agius4/ionic,driftyco/ionic,TillaTheHun0/ionic,driftyco/ionic,alan-agius4/ionic,alan-agius4/ionic,alan-agius4/ionic,TillaTheHun0/ionic,alan-agius4/ionic,alan-agius4/ionic,driftyco/ionic,driftyco/ionic,TillaTheHun0/ionic,driftyco/ionic